The development of penicillin started – but definitely did not end – with the chance discovery of some mold in a petri dish. There is so much more to the story.
Research:

Robert Moses and the Shaping of New York, Part 2
42:12

Robert Moses and the Shaping of New York, Part 1
41:59

SYMHC Classics: Eradication of Smallpox
43:25